As one of Earth's closest neighbors in space, Mars has long captivated humans with the prospect of alien life located just a short rocket trip away. No such life has been found. But now, as NASA and other space agencies have begun to explore the skies and surface of the Red Planet using robotic technology, images of strange features and formations continue to inflame skywatchers' hopes, fears and curiosities.
Here are some of our favorite objects on Mars that look like they don't belong on a dead and dusty planet. Many of these are a result of pareidolia — the tendency for humans to seek familiar patterns and shapes in inanimate objects. However, some of them may even lead scientists to the long-sought evidence of past Martian life.
An open "travel book"
Perhaps weary from hunting for evidence of ancient water, NASA's Curiosity rover took a short break in April 2023 to leaf through the pages of an old Martian hardback lying in the dust of Gediz Vallis. While the strange object may look like a book with a single page frozen mid-turn, it is in fact just a rock — and a small one at that. The charming little book-rock measures just 1 inch (2.5 centimeters) wide, according to NASA. Hey, at least it's travel-size!
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A "teddy bear's face"
In an image shared in January 2023 by the University of Arizona (UA), what appears to be the face of an enormous Martian teddy bear — complete with two beady eyes, a button nose and an upturned mouth — grins at the camera of NASA's Mars Reconnaissance Orbiter. According to UA, the cuddly-wuddly formation is likely just a broken-up hill in the center of an ancient crater. But as far as we're concerned, it's the cutest pile of rubble in the known universe.
Frozen "mineral flowers"
Branching outward like a tiny coral, this delicate mineral flower is about the closest thing to greenery one can find on the Red Planet today. Mineral deposits like these are common sights across Mars and result from ancient water mixing with ancient rock. Still, it's rare to see a deposit that's so perfectly flower-like, NASA researchers said. You'll notice two slightly less impressive, circular rocks of the same type to the right of the coral. Curiosity spotted this floral feature in February 2022.
A mysterious "doorway"
Is this perfectly hewn "doorway" into a Martian cliffside evidence of intelligent alien life on the Red Planet — or perhaps signs of a secret society of human astronauts camped out in clandestine Mars bunkers? Sadly (for conspiracy theorists), the truth is far simpler: It's just an eroded rock formation caught at the perfect angle. The image was captured by NASA's Curiosity rover in 2022.
Fossilized "animal tracks"
Did alien creatures once skitter across the surface of Mars, leaving fossilized tracks embedded in the rocks? One researcher made this controversial claim in 2018, pointing to images of stick-like structures, each about the size of a grain of rice, crisscrossing a Martian rock. NASA researchers quickly debunked the claims, noting that similar features are plentiful on Earth in areas where salts become concentrated in water, such as evaporating lakes. Their presence on Mars is yet more evidence of past rivers and lakes on the Red Planet, but they offer no proof that living creatures ever adorned its surface.
A bushel of "blueberries"
Blueberries are not a significant source of iron when consumed on Earth — but these geological "blueberries" discovered by NASA's Opportunity rover on Mars in 2004 are built differently. The iron-rich spheres, polished smooth by plentiful amounts of water billions of years ago, are some of the earliest evidence scientists have of Mars once being an incredibly wet world. Whether they also taste good on cheesecake is a question for future generations to grapple with.
Thousands of black "spiders on Mars"
Every spring, thousands of squiggly black "spiders" emerge from their hibernation near the Martian south pole. No, they are not real spiders — they are not alive at all, of course. The seasonal phenomenon is a result of buried carbon dioxide ice sublimating, or turning to gas, as the weather warms. The newly released gas bursts through layers of surface ice, carrying with it dark dust that splatters across the ground in craggy patterns. To be visible from space, as these formations are, the "spiders" must be fairly big — each one measuring 150 to 3,300 feet (45 meters to 1 kilometer) across, according to the European Space Agency (ESA). Please, nobody tell Ziggy Stardust the bad news.
Ruins of an "Inca City"
Near the Martian south pole are curious structures that look like the ruins of a vast and ancient city. Dubbed the "Inca City" for its resemblance to actual ruins discovered in South America, the bizarre rock formation may be made of elevated sand dunes that turned to stone over time, according to ESA. However, its exact origins remain a mystery. The labyrinthine formation appears to curve, forming part of a giant circle 53 miles (86 km) in diameter, leading scientists to suspect it may be part of a much larger impact crater from a meteor strike ages ago.
An ancient smiley face
Did someone spray-paint a grinning face onto the Martian surface? Not quite, despite what it looks like in this infrared image snapped by ESA's ExoMars Trace Gas Orbiter. Visible only under certain conditions, the face seen here is actually the remnants of an ancient lake, outlined by chloride salt deposits and dotted with two meteor crater eyes. While no Martian graffiti artists are going to pop up from the lake to claim their work, the face-like structure could contain evidence of ancient life on the Red Planet. As Mars' once-plentiful lakes dried up, the remaining water sources likely became very salty, possibly offering a haven for microbial life.
An extremely out-of-place rock
One of these things is not like the other. Standing out like a sore Martian thumb inside dusty Jezero Crater, this unusually white rock is the first of its kind ever seen on the Red Planet. Dubbed "Atoko Point" after a similarly light-colored feature of the Grand Canyon, the speckled rock is likely made of the minerals pyroxene and feldspar, according to an analysis by NASA's Perseverance rover. How did such a white rock find itself in such dark-hued company? It likely tumbled down from the crater rim or was transported to the crater floor from elsewhere on Mars back when rivers raged across the region.
A stony "Star Trek" symbol
Looks like someone from Starfleet left their communicator badge on the Red Planet — or so it would appear from the familiar shape of this rock spotted by the Curiosity rover. The rock's delta shape is just a coincidence, according to NASA. It is one of thousands located on Mount Sharp, which Curiosity has been exploring for years in its search to uncover clues about Mars' past and whether it ever held the conditions for life.
A "tile floor"
While scaling the slopes of Mount Sharp in 2021, NASA's Curiosity rover found remnants of what looks like a tile floor from a Martian bathroom. Dozens of interlocked polygons cracked through the dirt; most contain five or six sides and date to between 3.8 billion and 3.6 billion years ago. These jagged polygons are mud cracks, which have repeatedly dried out and moistened again over the course of untold years. They likely date to a time when the water level in the surrounding Gale Crater rose and fell repeatedly, causing the polygonal cracks in the ground to appear and disappear over time before a final dry spell left them as they are today.
Perfectly circular sand dunes
Mars is covered in dunes of all shapes and sizes, but few of them are as perfectly circular as the group spotted above by NASA's Mars Reconnaissance Orbiter in 2022. Snapped while flying over Mars' northern hemisphere, the image shows a bubbling patchwork of dark and strangely round dunes, slanting southward in the direction where the Martian wind likely blew them. Scientists are still not certain why these particular dunes are so circular or why they appear to be slowly migrating away from Mars' equator at a rate of roughly 3.3 feet (1 m) per Martian year (687 days on Earth).
A "shark fin" and a "crab claw"
While trawling through Jezero Crater, NASA's Perseverance rover caught sight of a few fishy-looking rocks. The two odd boulders — one jutting upward like a shark fin, and the other crimped like a crab claw — surprised researchers. However, there isn't much mystery to them. They are just rocks, sculpted by the wind over billions of years and left in the Martian dust for pattern-seeking human minds to find.
A "floating spoon"
In 2015, NASA's Curiosity rover spotted what appeared to be a wooden spoon, floating in midair with a shadow on the ground beneath it. It was, of course, an optical illusion; the spoon is simply a rock, shaped by the wind over eons, also known as a ventifact. The handle of the spoony rock juts out from a larger formation, allowing the spoon's rounded tip to hover over the ground below, casting a distinct shadow beneath it.
An eerie "face"
One of the earliest Martian rock formations to capture the public's interest was this infamous "face" spotted by NASA's Viking 1 satellite in 1976. While circling the planet looking for a landing site for its robotic companion, Viking 2, the satellite spotted a mound of rocks, partially obscured in shadow, distinctly resembling a human face. Follow-up observations with later spacecraft showed that the face was visible only from certain angles and under certain light conditions, proving that the Martian mound's humanlike appearance was just a trick of light and shadow.
A "giant's fingerprint"
A long time ago, something slammed into the surface of Mars and left this enormous, ridged, thumbprint-like depression behind. A giant finger was not the culprit, of course. Located inside a much larger crater called Airy-0, this Martian hole is the result of an ancient meteor impact. The bright striations forming the "lines" of the fingerprint are a common sight across Mars. Known as transverse aeolian ridges, they are created when sand dunes get coated in a thin layer of dust. The dust likely contains reflective minerals, giving the depression its glowing appearance in this image.
A rock with an, er … crack
Try not to laugh at this rock snapped by NASA's Perseverance rover in 2021. The cracked boulder became the butt of more than a few jokes after its close-up was first released to the public. There's really not much to see, though — the Red Planet is full of cracked rocks, albeit not quite as plump as this one. Perseverance spotted this rock in dusty Jezero Crater, on its 102nd day on Mars.
An "angel" and a heart
When it's summertime on Mars, the angels come out to play. The Martian south pole is usually covered in an enormous ice cap, but when the ice melts in warmer weather, patterns in the ancient, red-hued sediment below come to light. This image, snapped by ESA's Mars Express spacecraft, shows an angel-like pattern next to a heart-shaped one. Both of these familiar-looking structures are the result of meteor impact craters that scraped away Mars' dusty topsoil to reveal the darker sediment below.
A weirdly green rock with "drill holes"
Did a bored Martian teenager get a hold of his parents' power tools again? That is one (unlikely) explanation for a strange, green rock seemingly pumped full of drill holes that was spotted by NASA's Perseverance rover early in its mission. The roughly 6-inch (15 cm) rock looks out of place in its environment, and scientists aren't totally sure how to explain it. Perhaps it is the remnant of a meteor that collided with the Red Planet, or maybe it is a piece of Martian bedrock that was flung far across the world during an impact event. Most of the holes are also a mystery — but, if you look just right of center, you may see a small train of tiny, uniform pockmarks left by Perseverance's laser, which it fired at the rock while trying to analyze its composition.
A small "foreign object"
A small, rectangular object spotted in Mars' Gale Crater in 2018 briefly gave NASA scientists a scare. Looking vaguely like a dusty sheet of metal, the object was potentially thought to be a chunk of the Curiosity rover that had inexplicably fallen off. Luckily, a quick analysis showed that the "foreign object," as NASA initially dubbed it, was just a flake of rock that had split off of a larger formation and wasn't foreign to Gale Crater at all.
A strange, white tower
Towering over the Martian horizon in an image captured by NASA's Perseverance rover in 2023, a tall, white column stands against the dark, rocky background. It is, in fact, a Martian dust devil. And it's an enormous one: The dusty vortex captured here is taller than an average tornado on Earth and five times taller than the Empire State Building, according to NASA. Formed when rising cells of warm air meet falling columns of cool air, dust devils are exceedingly common on Mars — perhaps numbering as many as 145 million per day, one 2018 study estimated.
A "scar" longer than the Grand Canyon
Gaping like a fresh wound in this image captured by ESA's Mars Express orbiter in 2024, the Martian feature known as Aganippe Fossa is a sight to behold. The deep, dark ravine stretches around 375 miles (600 km) long — longer than the Grand Canyon, which measures about 277 miles (446 km) long. Located near the base of an extinct volcano, the Martian canyon likely formed as the result of ancient volcanic activity — possibly when a large pool of magma beneath the volcano pushed violently upward, tearing the ground asunder, according to ESA.
"Rock candy," or ultra-rare crystals?
These strangely colored crystals on Mars were discovered by pure accident. In May 2024, NASA's Curiosity rover drove over a small rock in its path, unintentionally crushing it. Buried within the stone tomb was a cache of rare minerals, including some never seen before on the Red Planet. The yellowish crystals are made of pure elemental sulfur. Scientists had long expected that this material existed on Mars but had no proof until Curiosity's bout of destructive driving.
A "bullet" hole
What looks like a hole blasted into the Martian landscape by a stray bullet may be something much more exciting — a possible refuge for future astronauts. The hole, which measures a few meters across, was imaged by NASA's Mars Reconnaissance Orbiter in 2022 on the flank of a massive volcano called Arsia Mons. The pit is located along a lava flow and appears to be a vertical shaft that could potentially connect to a deep system of caverns below the volcano. Although the hole's depth is unknown, it may be a tempting refuge for future astronauts who need a place to shield themselves from the intense radiation that beams down on the Red Planet.
An underground "dog"
Strange structures don't appear only on Mars' surface but underground as well. In September 2024, researchers combined data from several Mars-orbiting spacecraft to create a planet-wide map of gravitational anomalies — places where the pull of gravity is stronger than average, suggesting the presence of massive, dense structures located under the planet's surface. Most of these dense blobs are amorphous, but one caught the researchers' attention: a strange, dog-shaped structure, with a dark tail and ears, located near the Martian north pole. It's unclear how the dense, doggy structure formed, but it could be related to a past meteor impact or a pile-up of volcanic material.
Debris from outer space?
Nestled among the dusty, red rocks of Gale Crater, a jagged, gray object instantly caught the attention of scientists operating NASA's Curiosity rover. The shrapnel-like rock looks out of place because it almost certainly is — according to researchers, the pointy boulder is probably the remnant of a meteorite that crash-landed on Mars' surface ages ago. Dubbed Ames Knob and measuring about 4 inches wide by 5.5 inches long (10 by 14 cm), this meteorite isn't just space trash; according to NASA researchers, studying the rock could help reveal the past conditions on the planet when the meteorite fell, including whether it landed on land or in now-vanished water.
Debris … from Earth?
In 2022, NASA spotted what looked like the wreck of an "alien" spacecraft on Mars. In this case, the "aliens" were, in fact, Earthlings; the wreckage seen by NASA's Ingenuity Mars helicopter was a piece of the helicopter's own parachute and backshell, a saucer-like cover that helped slow the robotic craft's descent as it dropped onto the Red Planet along with the larger Perseverance rover. This piece of wrecked human technology, photographed by Ingenuity while it was flying 26 feet (8 m) above the Martian surface, looks particularly alien amid the desolate rocks and dust of the surrounding landscape.
An alien "egg"?
From certain angles, this pockmarked rock looks like an oozing, green egg belonging to some unknown alien monster. But a quick analysis from NASA's Curiosity rover revealed that the odd boulder — dubbed Egg Rock — is actually a fragment of a meteorite that landed on the Red Planet at some unknown time in the past. Studying Martian meteorites like this one can reveal valuable clues about the planet's past but is unlikely to lead back to any extraterrestrial monster nests.
Swirling patterns
Strange patterns carved into the surface of Mars' Nili Fossae region aren't alien sand art or the Martian version of Peru's Nazca Lines. They are, in fact, mineral deposits containing large quantities of olivine, a mineral typically only found deep below the surface of Mars. How did so much olivine-rich rock reach the planet's surface? That question presents a tempting mystery for scientists. It could be that a huge asteroid impact excavated the Martian interior, bringing olivine to the surface in swirling splatters — or perhaps the subsurface mineral saw daylight following a massive volcanic eruption. Its precise origin remains a mystery to this day.
An alien monolith?
When amateur stargazers were looking through images from NASA's Mars Reconnaissance Orbiter, they spotted something strange in the satellite's data: a bizarrely rectangular object reminiscent of the alien monolith from the opening scene of "2001: A Space Odyssey." The perplexing feature is indeed monolithic in shape and size, according to mission scientists. However, it is likely nothing more than a big, perfectly rectangular rock.
A crawling robot
Spotted from miles above by NASA's Mars Reconnaissance Orbiter, a crawling metallic robot glints on the Martian surface far below. This is a rare case where the mystery object is exactly what it looks like; that robot is NASA's Curiosity rover, making its way up Mount Sharp several years into its mission to explore the Red Planet. Concrete evidence that Mars ever held life is still lacking — but at least we can say Mars is the only known planet in the universe inhabited exclusively by robots.
